In the winter of 1999 the US Deep Caving Team Inc. launched a major mapping project of the massive underwater cave system of Wakulla Springs located in North Florida's panhandle. The team brought together some of the most experienced cave divers from allover the world. Under the direction of Dr. Bill Stone, the team used cutting edge diving equipment including: closed circuit mixed gas rebreather technology, diver propulsion systems, lighting systems, as well as new 3D digital mapping technology. Even as the project progressed, innovative modifications to life support, propulsion, and lighting systems were continually required to support divers working in one of one earth's most technically demanding and dangerous environments. Using a commercially available decompression habitat and personnel transfer capsule, the mapping and exploration teams were able to complete the lengthy decompression schedules associated with three to five hour excursions at 100 meters depth in relative comfort. During the course of the project, three diving related accidents occurred. In all three cases the incidents occurred due to the diver either ignoring or forgetting written safety procedures and protocols. Even though most of the technologies used in this endeavor were far and away the most advanced ever used in mapping an underwater cave system, human physiology was continuously being tested to its limits. The technologies and techniques developed during the Wakulla 2 Project will likely become the future standard for extreme, scientific, and exploration related diving.